This is despite the "Big Five" - HSBC, Barclays, Halifax Bank of Scotland, Lloyds TSB and Royal Bank of Scotland - making combined profits of #41.3billion in the past year. That's #131 a second.

Reader Phil Hartney was the victim of one of these sly money spinners. When he opened his Virgin Money credit card statement he was stunned to find he had been hit with a #10 charge - for being #12.72 in credit.

Phil, 54, of Glossop, Derbys, said: "This seems wrong. I was amazed I could be made to pay for keeping my account in good order. I keep this card for emergencies. I don't want to owe anything, so I left it in credit. It's unfair to sting me."

He has been trapped by the latest fee - a credit balance service charge. Any Virgin Money customer with a positive balance on a card for more than 12 months will be charged #10.

A Virgin spokesman said: "It costs us money to send out statements and look after these accounts.

"We're not making money out of people with positive balances. But you only pay this fee if you have been in credit for the full 12 months and customers were warned it was coming."

The banks' attempts to boost their profits comes as the Office of Fair Trading launched a probe into the cost of current accounts.

The watchdog has demanded that the banks come clean over how much customers really pay for "free" banking.

And it follows an earlier demand that credit card charges for those who miss a payment or bust their credit limits should be lowered.

Virgin is not alone in inventing new charges. Credit card giant MBNA has whacked a #10 fine on customers who keep their cards in credit for 12 months.

And Lloyds TSB has made those who failed to use their card "regularly" fork out #35. Lloyds and MBNA claim that only a small fraction of their customers were hit by this fee.

But Lloyds refused to say how long customers could go without using their card without being hit by the penalty.

Its means existing cardholders have no idea whether they will be stung by the fee in the future.

The Banking Code Standards Board, which oversees fair play, said Lloyds was in the clear because it gives customers 30 days in which either to use the card or close their account.

But this will be little comfort to account holders who are being kept in the dark over how to avoid incurring the charge in future.

Other banks maintain their profits in a different way.

Co-op and Northern Rock started charging customers #2 a month following the OFT demand that late payment fees had to be dropped to around #12.

Now Your Money can reveal Morgan Stanley is to follow suit. Customers on its Black card - which is aimed at people with a history of debt - have been sent letters saying they had to pay #20 a year.

David Kuo, head of personal finance at comparison site Fool.co.uk, said: "Some of the practices we have seen, especially in the credit card market, are downright devious and prey on vulnerable customers.

"These tactics belong in sleazy Soho clip-joints rather than high street banks. Banks must learn to be more open and honest, so customers can make informed choices."

To avoid paying these charges you must keep an eye on your monthly statements.

Under the Banking Code you have 30 days notice to contest the charges.

If you do not get this, complain to the bank directly. If necessary, threaten to close your account. If that does not work take it up with the Financial Ombudsman Service.